release/18.x: [Support] Fix color handling in formatted_raw_ostream (#86700)

[llvmbot]

Backport c9db031

Requested by: @nga888

[llvmbot]

@JDevlieghere What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-llvm-binary-utilities

@llvm/pr-subscribers-llvm-support

Author: None (llvmbot)

Changes

Backport c9db031

Requested by: @nga888

---

Full diff: https://github.com/llvm/llvm-project/pull/86940.diff

4 Files Affected:

• (modified) llvm/include/llvm/Support/FormattedStream.h (+44-7)
• (modified) llvm/lib/Support/FormattedStream.cpp (+3)
• (modified) llvm/tools/llvm-mc/llvm-mc.cpp (-5)
• (modified) llvm/tools/llvm-objdump/llvm-objdump.cpp (-7)

diff --git a/llvm/include/llvm/Support/FormattedStream.h b/llvm/include/llvm/Support/FormattedStream.h
index 5f937cfa798408..850a18dbb94121 100644
--- a/llvm/include/llvm/Support/FormattedStream.h
+++ b/llvm/include/llvm/Support/FormattedStream.h
@@ -52,6 +52,10 @@ class formatted_raw_ostream : public raw_ostream {
   /// have the rest of it.
   SmallString<4> PartialUTF8Char;
 
+  /// DisableScan - Temporarily disable scanning of output. Used to ignore color
+  /// codes.
+  bool DisableScan;
+
   void write_impl(const char *Ptr, size_t Size) override;
 
   /// current_pos - Return the current position within the stream,
@@ -89,9 +93,33 @@ class formatted_raw_ostream : public raw_ostream {
       SetUnbuffered();
     TheStream->SetUnbuffered();
 
+    enable_colors(TheStream->colors_enabled());
+
     Scanned = nullptr;
   }
 
+  void PreDisableScan() {
+    assert(!DisableScan);
+    ComputePosition(getBufferStart(), GetNumBytesInBuffer());
+    assert(PartialUTF8Char.empty());
+    DisableScan = true;
+  }
+
+  void PostDisableScan() {
+    assert(DisableScan);
+    DisableScan = false;
+    Scanned = getBufferStart() + GetNumBytesInBuffer();
+  }
+
+  struct DisableScanScope {
+    formatted_raw_ostream *S;
+
+    DisableScanScope(formatted_raw_ostream *FRO) : S(FRO) {
+      S->PreDisableScan();
+    }
+    ~DisableScanScope() { S->PostDisableScan(); }
+  };
+
 public:
   /// formatted_raw_ostream - Open the specified file for
   /// writing. If an error occurs, information about the error is
@@ -104,12 +132,12 @@ class formatted_raw_ostream : public raw_ostream {
   /// underneath it.
   ///
   formatted_raw_ostream(raw_ostream &Stream)
-      : TheStream(nullptr), Position(0, 0) {
+      : TheStream(nullptr), Position(0, 0), DisableScan(false) {
     setStream(Stream);
   }
-  explicit formatted_raw_ostream() : TheStream(nullptr), Position(0, 0) {
-    Scanned = nullptr;
-  }
+  explicit formatted_raw_ostream()
+      : TheStream(nullptr), Position(0, 0), Scanned(nullptr),
+        DisableScan(false) {}
 
   ~formatted_raw_ostream() override {
     flush();
@@ -136,17 +164,26 @@ class formatted_raw_ostream : public raw_ostream {
   }
 
   raw_ostream &resetColor() override {
-    TheStream->resetColor();
+    if (colors_enabled()) {
+      DisableScanScope S(this);
+      raw_ostream::resetColor();
+    }
     return *this;
   }
 
   raw_ostream &reverseColor() override {
-    TheStream->reverseColor();
+    if (colors_enabled()) {
+      DisableScanScope S(this);
+      raw_ostream::reverseColor();
+    }
     return *this;
   }
 
   raw_ostream &changeColor(enum Colors Color, bool Bold, bool BG) override {
-    TheStream->changeColor(Color, Bold, BG);
+    if (colors_enabled()) {
+      DisableScanScope S(this);
+      raw_ostream::changeColor(Color, Bold, BG);
+    }
     return *this;
   }
 
diff --git a/llvm/lib/Support/FormattedStream.cpp b/llvm/lib/Support/FormattedStream.cpp
index c0d28435099570..c50530e76efc0a 100644
--- a/llvm/lib/Support/FormattedStream.cpp
+++ b/llvm/lib/Support/FormattedStream.cpp
@@ -94,6 +94,9 @@ void formatted_raw_ostream::UpdatePosition(const char *Ptr, size_t Size) {
 /// ComputePosition - Examine the current output and update line and column
 /// counts.
 void formatted_raw_ostream::ComputePosition(const char *Ptr, size_t Size) {
+  if (DisableScan)
+    return;
+
   // If our previous scan pointer is inside the buffer, assume we already
   // scanned those bytes. This depends on raw_ostream to not change our buffer
   // in unexpected ways.
diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index cf6aaa1f06981f..2754d49645595d 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -547,11 +547,6 @@ int main(int argc, char **argv) {
     std::unique_ptr<MCAsmBackend> MAB(
         TheTarget->createMCAsmBackend(*STI, *MRI, MCOptions));
     auto FOut = std::make_unique<formatted_raw_ostream>(*OS);
-    // FIXME: Workaround for bug in formatted_raw_ostream. Color escape codes
-    // are (incorrectly) written directly to the unbuffered raw_ostream wrapped
-    // by the formatted_raw_ostream.
-    if (Action == AC_CDisassemble)
-      FOut->SetUnbuffered();
     Str.reset(
         TheTarget->createAsmStreamer(Ctx, std::move(FOut), /*asmverbose*/ true,
                                      /*useDwarfDirectory*/ true, IP,
diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 22b427f57658e1..7ecdd60313d065 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -2032,13 +2032,6 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
 
       formatted_raw_ostream FOS(outs());
 
-      // FIXME: Workaround for bug in formatted_raw_ostream. Color escape codes
-      // are (incorrectly) written directly to the unbuffered raw_ostream
-      // wrapped by the formatted_raw_ostream.
-      if (DisassemblyColor == ColorOutput::Enable ||
-          DisassemblyColor == ColorOutput::Auto)
-        FOS.SetUnbuffered();
-
       std::unordered_map<uint64_t, std::string> AllLabels;
       std::unordered_map<uint64_t, std::vector<BBAddrMapLabel>> BBAddrMapLabels;
       if (SymbolizeOperands) {

[JDevlieghere]

LGTM

[tstellar]

Hi @nga888 (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix.

[nga888]

Hi @nga888 (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix.

Fix color handling for buffered formatted_raw_ostream which allows the unbuffered workaround in llvm-objdump to be removed, restoring the performance of llvm-objdump disassembly when the output is redirected.